This invention relates to an article, system and method used for creating an identification marker in the form of an image used for authentication of documents.
Recent advances in optics provide for a method of exposure of materials on a length scale much smaller than previously realized. Such near-field optical methods are realized by placing an aperture or a lens in close proximity to the surface of the sample or material to be exposed. Special methods for positioning control of the aperture or lens are required, as the distance between the optical elements (aperture or lens) is extremely small. Betzig and Trautman in U.S. Pat. No. 5,272,330 reported on the use of tapered optical fibers as a means of providing exposures in extremely small areas; exposures of the size of 10 nm in area are now relatively commonplace. In this case, the fiber tip position is maintained to be within some nanometers (typically 10-50) of the target surface. Others (see, for example, the review by Q. Wu, L. Ghislain, and V. B. Elings, Proc. IEEE (2000), 88(9), pg. 1491-1498) have developed means of exposure by the use of the solid immersion lens (SIL). The SIL is positioned within approximately 0.5 micrometer of the target surface by the use of special nano-positioning technology as in the case of the tapered optical fiber. SIL technology offers the advantage that the lens provides a true imaging capability, i.e. features in a real object can be faithfully rendered in an image of reduced spatial extent. In the case of the SIL images can be produced much smaller than the image size achievable through the use of conventional or classical optics. Such conventional optics are said to be diffraction-limited because the size of the smallest feature in an image is limited by the physical diffraction. Exposures produced by means of the SIL or other near-field optical methods can be much smaller in spatial extent than those produced by conventional optical systems and still be readable. Near-field optics have been used to create single dots and used to capture images not capable of being captured using a conventional optical microscope. The prior art does not teach forming an entire image using near-field optics. Such near-field technology is used in the present invention to provide a means of exposure to be used in the production of small images and to use these images as indicia for the purpose of authentication.
In accordance with one aspect of the present invention there is provided a method of making a discrete micro image product, comprising the steps of:
providing a first product, applying a plurality of micro discrete image products, each of the micro discrete image products having a size no greater than about 20 microns and having at least one predetermined image thereon, said predetermined image having a size no greater than about 10 microns.
In accordance with another aspect of the present invention there is provided a method of making a discrete micro image product, comprising the steps of:
providing a photosensitive media capable of receiving an image thereon;
providing a plurality of micro discrete images on the media, the micro discrete images being no larger than about 20 microns; and
forming the media into a plurality of micro discrete particles each having a size not greater than about 20 microns so that the discrete images can be discerned from the particles.
In accordance with yet another aspect of the present invention there is provided a product having a plurality of micro discrete particles placed thereon, the particles having a size no greater than about 20 microns and having at least a portion of a micro image placed thereon, the micro image having a size no greater than about 20 microns.
In still another aspect of the present invention there is provided a micro discrete particle having a size no greater than about 20 microns and having photosensitive layer on which at least a portion of a micro image is formed thereon, the micro image having a size no greater than about 20 microns.
These and other aspects, objects, features, and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.